 /*******************************************************************************
  * Copyright (c) 2000, 2005 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/

 package org.eclipse.ui.contexts;

 /**
  * An instance of this interface is an context as defined by the extension point
  * <code>org.eclipse.ui.contexts</code>.
  * <p>
  * An instance of this interface can be obtained from an instance of
  * <code>IContextManager</code> for any identifier, whether or not an context
  * with that identifier is defined in the extension registry.
  * </p>
  * <p>
  * The handle-based nature of this API allows it to work well with runtime
  * plugin activation and deactivation. If a context is defined, that means that
  * its corresponding plug-in is active. If the plug-in is then deactivated, the
  * context will still exist but it will be undefined. An attempts to use an
  * undefined context will result in a <code>NotDefinedException</code> being
  * thrown.
  * </p>
  * <p>
  * This interface is not intended to be extended or implemented by clients.
  * </p>
  *
  * @since 3.0
  * @see org.eclipse.ui.contexts.IContextManager
  * @see org.eclipse.core.commands.contexts.Context
  * @deprecated Please use the "org.eclipse.core.commands" plug-in instead.
  */
 public interface IContext extends Comparable {

     /**
      * Registers an instance of <code>IContextListener</code> to listen for
      * changes to properties of this instance.
      *
      * @param contextListener
      * the instance to register. Must not be <code>null</code>. If
      * an attempt is made to register an instance which is already
      * registered with this instance, no operation is performed.
      */
     void addContextListener(IContextListener contextListener);

     /**
      * Returns the identifier of this instance.
      *
      * @return the identifier of this instance. Guaranteed not to be
      * <code>null</code>.
      */
     String getId();

     /**
      * Returns the name of this instance suitable for display to the user.
      * <p>
      * Notification is sent to all registered listeners if this property
      * changes.
      * </p>
      *
      * @return the name of this instance. Guaranteed not to be <code>null</code>.
      * @throws NotDefinedException
      * if this instance is not defined.
      */
     String getName() throws NotDefinedException;

     /**
      * Returns the identifier of the parent of this instance.
      * <p>
      * Notification is sent to all registered listeners if this property
      * changes.
      * </p>
      *
      * @return the identifier of the parent of this instance. May be
      * <code>null</code>.
      * @throws NotDefinedException
      * if this instance is not defined.
      */
     String getParentId() throws NotDefinedException;

     /**
      * Returns whether or not this instance is defined.
      * <p>
      * Notification is sent to all registered listeners if this property
      * changes.
      * </p>
      *
      * @return true, iff this instance is defined.
      */
     boolean isDefined();

     /**
      * Returns whether or not this instance is enabled.
      * <p>
      * Notification is sent to all registered listeners if this property
      * changes.
      * </p>
      *
      * @return true, iff this instance is enabled.
      */
     boolean isEnabled();

     /**
      * Unregisters an instance of <code>IContextListener</code> listening for
      * changes to properties of this instance.
      *
      * @param contextListener
      * the instance to unregister. Must not be <code>null</code>.
      * If an attempt is made to unregister an instance which is not
      * already registered with this instance, no operation is
      * performed.
      */
     void removeContextListener(IContextListener contextListener);
 }

